From the new WizardUniverse site's article on the new Geoff Johns/Alex Ross Justice Society of America series in October comes word (via Johns himself) of some of the characters to appear, including an apparently new Starman - or rather, what would seem to be the appearance of an old one from the future.
“Who is Opal City’s new hero? Where is he from? Why is he here? He might not even know for sure, but he’s hoping the Justice Society can tell him.”
From the last page of Infinite Crisis 7, the new Starman will be wearing the full bodysuit starfield costume as seen in Kingdom Come and the last issue of Starman. Speaking of which, here's the dialogue from pages 2-5 of that issue (#80, August 2001), which suggests a lengthy stay by this particular Thom Kallor (but which would also imply that Stargirl doesn't keep the Cosmic Rod).
Remember that Jack "Starman" Knight met Thom "Star Boy" Kallor (along with Shadow Lass) earlier in the Starman series, now Thom is all grown up.
- Jack: Thom Kallor. That is you under the mask?
- Thom: It is.
- Jack: So it's true. Everything. You will succeed me.
- Thom: One day, sure. But not today, tomorrow, nor the day after that. There's one who'll wield cosmic power before I will.
- Jack: Who?
- Thom: You know who. You've already made your selection, right?
- Jack: Yeah. But one day it'll be your turn.
- Thom: One day.
- Jack: And you're the reincarnation of Matt O'Dare and Brian Savage?
- Thom: H... Hold on. That's a new one. I'm reincarnated?
- Jack: Forget it. But everything will happen just like the Shade said?
- Thom: I'll return from the 31st Century. Yes. But whether your future leads to me, I can't say. I'm only one possible future, after all.
- Jack: Huh?
- Thom: The future isn't a straight route from the present like the present is to the past. The way ahead has many forks. Potential choices. Unsung songs. Unspoken verse. All awaiting the moment when "what might be" has become "what is".
- Jack: So... you're saying... I'm not sure what you're saying.
- Thom: For all I know in other possible futures, Thom Kallor died serving in the Legion. Or he turned evil. Or he was simply different enough in his personality he doesn't return to the past and become Starman. But in the future that's mine, I did.
- Jack: Do you regret it?
- Thom: I have lived such a full life in the 31st century even before coming here to begin again. It's as if I had two lives and no, I don't regret a moment, Jack.
- Jack: So, I'm back and I'm done. My time as Starman.
- Thom: Are you? Isn't there one more thing you forgot?
- Jack: Oh, yeah. I guess there is at that.
- Thom: It's me who's done.
- Jack: I don't understand.
- Thom: I remember how scared I was... as a boy... knowing the day I was destined to die? When I retun to my era that day will be tomorrow. Bringing you back from 1951 was the last thing I had to do.
- Jack: Oh, my God! If you know, couldn't you change your fate?
- Thom: I have lived, Jack. [Removes his mask for the first time, showing a scarred face.] More than enough. And I feel it was you who lit the way for me. Thank you. Good-bye.
- Jack: Well, if... err... I'm at a loss for words.
- Thom: Good-bye back at me will do.
- Jack: Good-bye, Thom. I'd wish you good luck too, but --
- Thom: Yeah, there wouldn't be much point. [Disappears with his Time Bubble.]